If your chemical tank is located outdoors, it’s exposed to the elements, such as sun, wind, and rain. Special considerations are recommended to protect the life of the storage tank, especially from damaging ultraviolet rays from the sun.
Extended UV exposure weathers your polyethylene storage tank prematurely. Without proper treatment or cover, the higher energy spectrum of the UV light causes a compound breakdown of the polyethylene elements, making the polyethylene tank material brittle.
When the tank becomes brittle, it can cause micro cracks, which lead to leaks and potential failure of the chemical storage tank.
Solutions to Reduce the Risk of Polyethylene Tank Exposure to UV
Let’s explore three different solutions to protect outdoor polyethylene storage tanks from UV damage.
Carbon Black Resin
Carbon Black is a nearly pure elemental carbon. When used as a resin in the molding of the polyethylene tank, it acts as an absorber of UV light. Adding Carbon Black is a simple, inexpensive solution to creating an internal stabilizer to your polyethylene chemical tank. The resin absorbs UV energy, transforms it into heat, and dissipates it throughout the tank.
While Carbon Black polyethylene tanks tend to have slightly higher temperatures than lighter colored or white polyethylene tanks, the UV protection outweighs the effects of the small increase in temperature. Carbon Black is the preferred pigment in higher-end applications, especially when storing harsh chemicals such as sodium hypochlorite.
Paint Your Own Tank
Painting the tank can reflect the UV rays and help reduce heating. If you paint your polyethylene tank, it's best to do it on-site. This allows the surface to oxidize a bit and also protect it from potential scratches during transportation and installation.
We recommend lightly bead-blasting the tank surface before painting, to ensure the paint adheres. You can also set the tank in the sun for a few months and allow the outer surface to oxidize naturally, then apply the paint.
If you choose to paint your chemical storage tank, be sure to follow proper procedures and to use a paint that won’t crack or flake with tank expansion. An acrylic or elastomeric paint, which expands and contracts with the tank, is best.
Painting a polyethylene tank is similar to painting the outside of a home or business. Paint can be applied in the traditional ways using airless sprayers, power sprayers, rollers, or even brushes but surface preparation is a key.
We’ve created a guide for painting polyethylene storage tanks to help you get the most out of your painted tank.
Insulation and Paint
If you’re located in a hot area like Arizona or Florida, we often recommend insulating the tank to protect it from ambient heat. Insulation does an excellent job of blocking UV rays while maintaining a cooler temperature of the chemical being stored. We apply two inches of insulation and a coating of industrial grade paint at the factory before the tank ships.
This is often an ideal solution for chemicals that degrade under higher temperatures, such as sodium hypochlorite.
Other Factors That Affect the Impact of UV on Polyethylene Tanks
Several other factors affect the impact that UV exposure has on polyethylene chemical storage tanks. The potential for leaks and tank failure increases with cycle times, frequent emptying and refilling, and multiple sidewall fittings on the tank. Microcracks tend to form where the tank is the weakest, at the tank fittings.
One solution to minimize the number of sidewall fittings and reduce the potential for microcracks is Poly Processing’s Integrally Molded Flanged Outlet (IMFO®) system. The IMFO System features a flange that is molded at the bottom sidewall while the tank is processing, making it a stress-free part of the tank. The flange is actually a part of the tank – it’s not an insert introduced during or after production. The one-piece construction enhances long-term performance of the tank, since it doesn’t compromise the tank hoop’s integrity or structural design.